| Research Abstract |
It is known that ultraviolet B light(UV) impairs the induction phase of contact hypersensitivity responses(CHS) and subsequently induces tolerance. Although this phenomenon has been appreciated for decades to be a major biological importance, immunological mechanisms underlying this event are not completely clear yet Dectin-2 is a new member of c-type lectin, which is selectively expressed on epidermal langerhans cells(LC). Here we examined roles of dectin-2 in UVB-induced immune tolerance of CHS. To do so, we first generated a soluble form of dectin-2(sDec2). sDec2 was generated by use of recombinant technology. Briefly, an extracellular domain of dectin-2 cDNA was subcloned to an expression vector, which was then transfected to and expressed in E.cli. Soluble recombinant protein was recovered from lysates of coli, purified and its inhibitory activity to cognate dectin-2 was ascertained in in vitro assays. To address the initial questions, sDec2 was injected to mice before either the
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induction or the elicitation of CHS. However, CHS was not affected regardless of the injection, indicating that dectin-2-mediated pathways are not involved in this event By contrast, if dectin-2 was injected to mice which was already UV exposed at 1,000J/m^2 for 4 consecutive days. Those mice were then hapten sensitized and challenged, leading to full outcome of CHS, while UV significantly suppressed CHS when those were only sensitized and challenged but not sDec2-injected. This indicates that dectin-2 is involved in the UV-mediated impairment of CHS. To check for its involvement in UV-induced tolerance, mice whose CHS were impaired by UV were left untreated for 14 days and then resensitized and rechallenged, resulting that CHS was significantly suppressed as compared to unexposed animals, indicating that tolerance was induced. However, sDec2-injection before the first sensitization restored CHS and did not lead to tolerance. Based on the fact that tolerance is mediated via generation of T suppressor cells(Ts), the above mentioned results indicate that dectin-2 mediates the induction of hapten specific Ts. This was further confirmed as sDec2-bound, but not unbound T cells impaired the induction of CHS upon transfer to naive recipients. To phenotypically characterize sDec2-bound Ts, FACS analysis was conducted, demonstrating that UV-induced Ts express CD4 and CD25 on their surface resembling currently hightlighted regulatory T cells(Ir). Tr are the re-nomenclatured Ts, which possess the ability to prevent the onset of autoimmune disorders, including type I diabetes mellitus or multiple sclerosis of murine models. Together, our study disclosed that UV-induced tolerance is mediated via generation of Tr, Less
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